1. Field of the Invention
The present invention relates to a liquid crystal display device and, in particular, to an active matrix liquid crystal display device.
2. Description of the Related Art
In active matrix liquid crystal display devices, each of regions that are formed on the liquid-crystal-side surface of one of transparent substrates opposed to each other with a liquid crystal interposed in between and that are enclosed by gate signal lines extending in the x direction and arranged in the y direction and drain signal lines extending in the y direction and arranged in the x direction is made a pixel region. Each pixel region is provided with a thin-film transistor that is driven being supplied with a scanning signal from one of the gate signal lines that define the pixel region and a pixel electrode that is supplied, via the thin-film transistor, with a video signal from one of the drain signal lines that define the pixel region.
Each of the above signal lines, thin-film transistors, pixel electrodes, etc. is formed by laying one on another a conductive layer, a semiconductor layer, and an insulating layer each of which is formed in a prescribed pattern by selective etching according to a photolithography technique.
As for recent high-resolution liquid crystal display devices, a problem of signal line disconnection is pointed out that occurs occasionally due to small signal line widths.
A technique for solving such a problem is disclosed in Japanese Patent Laid-Open No. 19294/1993. This technique prevents what is called a line defect that is caused by disconnection of a source signal line by forming, in each pixel, an electrical path of a source electrode (of a thin-film transistor)→a gate electrode (of the thin-film transistor)→a drain electrode (of the thin-film transistor)→a pixel electrode→a first conductor piece→a second conductor piece→a drain signal line by applying laser light to five locations, for example.
However, requiring two or more times of laser light application (specifically, five times more laser light) to repair a drain signal line, this technique has a problem that such work is cumbersome.
Since the first conductor piece and the second conductor piece need to be formed in each pixel region, this technique has another problem that the aperture ratio is lowered.
This technique has a further problem that point defects (pixel defects) are unavoidable though it can prevent line defects.